Download Adverse Weather Operations - Monsoon Training

Summer Monsoon regimes of the World
Monsoon winds from Southern Hemisphere
Global Pressure Pattern in July
Onset of Monsoon dates over India
Wind shears in Monsoon
•Monsoon means strong reversal of winds implying wind
shear conditions, creating a hazardous flight environ
•Winds at lower levels at 3000 to 5000 ft peninsular India
experiences low level Jet streams
Low Level Jet Stream in SW monsoon
Westerly Winds 20 knots
Aircraft suffers a ballooning effect
on account of low-level jet stream
Shear Zone
6000ft
Low level westerly jet stream of 40 knots and more
Temporary increase in airspeed giving a
greater lift and significantly reduce the rate of
decent and returning below the intended
decent
Opposite situations will occur in winter with inversion of temperature
over the helipad in association with foggy conditions
Shear Zone
Calm or light winds
Vertical/Slant visibility is deceptive
LATE CHIEF MINISTER, MR.Y.RAJASEKAR REDDY’S
HELICOPTER CRASH
http://www.youtube.com/watch?v=q3QeaKrdcXI&feature=fvwrel
Flight Regulation for Helicopters
• The helicopters are strictly expected to fly only under VMC.
•Due to circumstances beyond the control, sometimes the craft has to
enter the cloud.
•Hence some elementary knowledge of conditions for the formation of
clouds and their identification, to be refreshed by the participants is
desirable
The Formation of Clouds
Cloud formation is associated with rising air
Rising air cools adiabatically
The air reaches its dew point
Cloud is formed
The form (shape) of the cloud depends upon the stability of the
rising air
Layer (stratiform) cloud forms in stable air
Heaped (cumuliform) cloud forms in unstable air
Clouds can be categorized on the basis of the
“lifting mechanism” that is the process which
causes the air to move upwards
The formation of clouds
There are 4 categories:
•Convection cloud
•Orographic cloud
•Turbulence cloud
•Frontal cloud
Convection cloud
•Air is heated at the surface
•Air rises, cools adiabatically and reaches its dewpoint
•Cumulus or cumulonimbus cloud forms
Formation of convection cloud
Convection cloud
•Convection cloud can occur over land and sea
•It often forms when cold air from high latitudes is moving
southwards over the ocean
•The rising air currents are called thermals
Formation of Convection cloud
Orographic cloud
•Air meets high ground
•Air rises, cools adiabatically and reaches its dewpoint
•Cloud can be stratiform (stable air) or cumuliform (unstable air)
Formation of Orographic cloud
Orographic cloud
•The extent of the cloud depends upon
the extent of the high ground
•The height of the cloud is controlled by
the height at which it reaches its
dewpoint
•Famous orographic clouds include the
tablecloth and the levanter
Turbulence cloud
•The air is travelling across a colder surface
•The air moves upwards as part of the turbulence
•The air cools by conduction at the surface and adiabatically as it
rises
•The cloud formed is stratus cloud
Formation of Turbulence cloud
Stratus cloud
Cirrus cloud
Nimbostratus
Frontal cloud
•The warmer air rises upwards because it is less dense
•The rising air cools adiabatically and reaches its dewpoint
•The cloud will be Stform in stable air and Cuform in unstable air
Formation of frontal cloud: warm front
Formation of frontal cloud: cold front
Cloud Names
WMO System
Genera
e.g. Cirrus
Species
e.g.fibratus
Varieties
e.g. radiatus
Supplementary features
e.g. mamma
Cloud Names
Cirrus - Means a lock of hair
or a tuft of horsehair
Cumulus - Means an accumulation or a pile
Stratus- Means to spread out, to cover a layer
Nimbus – Means Rain
Cloud Classifications
•Height
•W.M.O.
•Form
•Formation
Classification by Height
High
Cloud Base 3 – 18 km
Medium
Cloud Base 2 – 8 km
Low
Cloud Base 0 – 2 km
Great Vertical Extent
Cloud Base 0 – 2 km
Stratocumulus
Genera
High Clouds
Cirrus
Cirrocumulus
Cirrostratus
Cirrus
Detached clouds in the form of
white, delicate filaments or white
or mostly white patches or
narrow bands. These clouds have
a fibrous (hair-like) appearance,
or a silky sheen, or both.
Cirrocumulus
Thin, white patch, sheet of layer
of cloud without shading,
composed of very small elements
in the form of grains, ripples, etc.
merged or separate, and more or
less regularly arranged, most of
the elements have an apparent
width of less than one degree.
Cirrostratus
Transparent, whitish cloud
veil of fibrous (hair-like) or
smooth appearance, totally
or partly covering the sky,
and generally producing
halo phenomena.
Genera
Medium Clouds
•Altocumulus
•Altostratus
•Nimbostratus
Altocumulus
White or grey, or both white and grey,
patch, sheet or layer of cloud,
generally with shading, composed of
laminae, rounded masses, rolls etc.
which are sometimes partly fibrous or
diffuse and which may or may not be
merged; most of the regularly
arranged small elements usually have
an apparent width between one and
five degrees.
Altostratus
Greyish or bluish cloud sheet or
layer of striated, fibrous or uniform
appearance, totally or partly
covering the sky, and having parts
thin enough to reveal the sun at
least vaguely, as through ground
glass. Altostratus does not show
halo phenomena.
Nimbostratus
Grey cloud layer, often dark, the
appearance of which is rendered
diffuse by more or less
continuously falling rain or snow,
which in most cases reaches the
ground.
It is thick enough throughout to
blot out the sun. Low, ragged
clouds frequently occur below the
layer, with which they may or may
not merge
Genera
Low Clouds
•Stratocumulus
•Stratus
Stratus
Generally grey cloud layer with a
fairly uniform base, which may give
drizzle, ice prisms or snow grains.
When the sun is visible through the
cloud, its outline is clearly
discernible. Stratus does not
produce halo phenomena except,
possibly, at very low temperatures.
Sometimes stratus appears in the
form of ragged patches.
Genera
Clouds of Great Vertical Extent
Cumulus
Cumulonimbus
Cumulus
Detached clouds, generally dense and
with sharp outlines, developing
vertically in the form of rising
mounds, domes or towers, of which
the bulging upper part often
resembles a cauliflower the sunlit
parts of these clouds are mostly
brilliant white, their base is relatively
dark and nearly horizontal.
Sometimes cumulus is ragged.
Cumulonimbus
Heavy and dense cloud, with a
considerable vertical extent, in the form of
a mountain or huge towers.
At least part of its upper portion is usually
smooth, of fibrous or striated, and nearly
always flattened; this part often spreads
out in the shape of an anvil or vast plume.
Under the base of this cloud which is often
very dark, there are frequently low ragged
clouds either merged with it or not, and
precipitation sometimes in the form of
virga .
Classification by Form
•Cirriform
•Cumuliform
•Stratiform
Cirriform
•High Cloud
•Tenuous
•Ice crystals
•Associated with depressions
Cumuliform
•Unstable Air
•Discrete clouds
•Vigorous upward motion
•Showers
Stratiform
•Stable Air
•Widespread
•Slow upward motion
•Continuous precipitation
The Importance of Dew point Temperature
During pre flight planning, if you find temperature and dew
point temperature are very close, you are bound to
encounter clouds
The cloud base will be around
(T– Td ) x 400 ft
The Difference between ceiling and base of cloud
The term ceiling is applicable when 5/8 or more is below
20,000 feet, otherwise the term base.
Reverting back to Monsoon Flying the following
slides can amplify the hazards of aviation
Sumai
Island
25 KTS
SW
WINDS
Runway highly
contaminated
due to heavy
rain
A passenger plane skidded off the runway and crashed into a building
after landing on the Thai resort island of Samui on Tuesday, killing the
chief pilot and injuring at least seven people including foreign tourists.
The Bangkok Airways flight landed in stormy weather and hit the airport's old
air traffic control tower, which had been converted into a fire station, said
Kanikka Kemawutanond, director-general of the Department of Civil Aviation.
The co-pilot and six tourists were hurt.
The Controls of Monsoon
 ITCZ
 Elnino
 Indian Ocean Dipolar Temperature effect
 The Effect of Mascrean high pressure area
 Madden Julian Oscillation
General Circulation
Animated circulation of global
winds
AIRFRANCE-447
ST
CRASH ON 1
JUNE 2009
PARIS
ETA 9UTC 1ST
JUNE
ATLANTIC
AFRICA
LAT 4N
LONG30W
CRASH 2UTC 1ST
JUNE
BRAZIL
RIO
DEP 22UTC
31ST MAY
ITCZ
EQ
CRASH
Extreme Turbulence
Radar is only an aid not an end by itself
• Contributing safety factors
- The crew did not detect an area of convective turbulence
(cloud), either visually or by radar.
- The aircraft penetrated an area of severe convective
turbulence.
- The area of convective turbulence encountered by the
aircraft comprised ice crystals.
- The aircraft radar had limited capability to detect cloud that
comprised ice crystals. [Minor safety issue]